The militant group has banned the teaching of all old curriculums at schools in Syria's Raqqa and Deir-ez-Zour governorates that are under its control.
United Nations Children’s Fund spokesman Christophe Boulierac told The Anadolu Agency that the militant group wanted schools that taught Islamic sharia law.
"Teaching the old curriculum is prohibited within ISIL territories," Boulierac said, using an abbreviation for the group.
"ISIL have suspended education in schools located in areas they control in Raqqa and Deir-ez-Zour until they complete the training for the teachers," he added.
He also said that numerous schools remained closed in the affected areas.
The militant group controls large swathes of territories in Syria and neighboring Iraq. The ongoing conflict and recent closure of some schools in Raqqa and Deir-ez-Zour and parts of rural Aleppo is believed to have disrupted education for around 670,000 children, according to the UN's agency for children.
He said that about 1.6 million children were out of schools since the outbreak of the Syrian civil war in 2011 that has so far claimed over 20,000 lives.
There were at least 68 attacks on schools across Syria in 2014 that killed at least 160 children.